1. Field of the Invention
The invention relates to the field of photography, and particularly to a photosensitive material processing apparatus.
2. Description of the Prior Art
The processing of photographic film involves a series of steps such as developing, bleaching, fixing, washing, and drying. These steps lend themselves to mechanization by conveying a continuous web of film or cut sheets of film or photographic paper sequentially through a series of stations or tanks, each one containing a different processing liquid appropriate to the process step at that station.
There are various sizes of photographic film processing apparatus, i.e., large photofinishing apparatus and microlabs. A large photofinishing apparatus utilizes tanks that contain approximately 100 litres of each processing solution. A small photofinishing apparatus or microlab utilizes tanks that may contain less than 10 litres of processing solution.
The chemicals contained in the photographic solution: cost money to purchase; change in activity and leach out or season during the photographic process; and after the chemicals are used the chemicals must be disposed of in an environmentally safe manner. Thus, it is important in all sizes of photofinishing apparatus to reduce the volume of processing solution. The prior art utilized various types of replenishing systems that add or subtract specific chemicals to the photographic solution to maintain a consistency of photographic characteristics in the material developed. It is possible to maintain reasonable consistency of photographic characteristics only for a certain period of replenishment. After a photographic solution has been used a given number of times, the solution is discarded and a new photographic solution is added to the tank.
Activity degradation due to instability of the chemistry, or chemical contamination, after the components of the photographic solution are mixed together causes one to discard the photographic solution in smaller volume tanks more frequently than larger volume tanks. Some of the steps in the photographic process utilize photographic solutions that contain chemicals that are unstable, i.e., they have a short process life. Thus, photographic solutions in tanks that contain unstable chemicals are discarded more frequently than photographic solutions in tanks that contain stable chemicals.
The prior art realized that if the volume of the various tanks contained within various sizes of photographic processing apparatus were reduced the same amount of film or photographic paper may be processed, while reducing the volume of photographic solution that was used and subsequently discarded.
Processing solutions are usually poured into the top of large tanks that comprise large photographic processing apparatus. Air is often trapped in the various tanks, conduits, pumps, filters, etc. of the large photographic processing apparatus. This trapped air causes an air lock, which does not allow the processing solution to be consistently circulated through the photographic processing apparatus. The above did not pose a major problem in large photofinishing apparatus since the trapped air had space to be eliminated from the top of the tank. The trapped air was eliminated from the filter by losing the top of the filter and allowing the air to escape with some of the processing solution. The conduits were large enough so that air was free to move through the conduits.
If processing solutions were poured into the top of smaller volume tanks the above problem was exacerbated. The smaller space caused more air to be trapped in the various components of the smaller photofinishing apparatus. If too much air was trapped the processing solution may become airbound and fail to circulate properly through the processing apparatus. A further problem is that the trapped air may break up into smaller air bubbles causing foaming or sudsing of the processing solution which results in non-uniform photosensitive development; excessive chemical oxidation and processing solution overflow.
As processing solution is added the viscosity, capillary action and meniscus interacting with the tank walls, conduits, filters, etc. prevents processing solution from displacing the air resident in the tank walls, conduits, filters, etc.
When processing solutions are pumped or drained from the various tanks, filters, conduits, pumps, etc. of large photographic processing apparatus portions of the processing solution and particulate matter are usually trapped in the tanks, filters, conduits, pumps, etc. of the photographic processing apparatus. If too much particulate matter is present in the photographic processing apparatus, the particulate matter will be recirculated back into the photosensitive material. This may streak and/or scratch the photosensitive material. The particulate matter may also become trapped in nozzles or orifices of the photographic processing apparatus restricting circulation of the processing solution. The above causes insufficient processing solution flow for proper reaction with the photosensitive material and nonuniform development of the photosensitive material.
The foregoing did not pose a major problem in large photographic processing apparatus, since the size of the various components of the photofinishing apparatus were large enough to allow the particulate matter to travel through the components of the photographic processing apparatus. However, in smaller volume photographic processing apparatus, the tanks, nozzles, orifices, etc. are not large enough to allow particulate matter to escape and circulate freely through the photographic processing apparatus.